Optical, XPS and XRD Studies of Semiconducting Copper Sulfide Layers on a Polyamide Film

Copper sulfide layers were formed on polyamide PA 6 surface using the sorption-diffusion method. Polymer samples were immersed for 4 and 5 h in 0.15 mol dm-3 K2S5O6 solutions and acidified with HCl (0.1 mol dm-3) at 20 degree C. After washing and drying, the samples were treated with Cu(I) salt solution. The samples were studied by UV/VIS, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods. All methods confirmed that on the surface of the polyamide film a layer of copper sulfide was formed. The copper sulfide layers are indirect band-gap semiconductors. The values of Ebg are 1.25 and 1.3 eV for 4 h and 5 h sulfured PA 6 respectively. Copper XPS spectra analyses showed Cu(I) bonds only in deeper layers of the formed film, while in sulfur XPS S 2p spectra dominating sulfide bonds were found after cleaning the surface with Ar+ ions. It has been established by the XRD method that, beside Cu2S, the layer contains Cu 1.9375 S as well. For PA 6 initially sulfured 4 h, grain size for chalcocite, Cu2S, was 35.60 nm and for djurleite, Cu 1.9375 S, it was 54.17 nm. The sheet resistance of the obtained layer varies from 6300 to 102 O/cm2.